1. Field
The disclosure relates to a carrier-attached copper foil, and more particularly to a copper foil attached with a carrier foil without a releasing layer and a method for manufacturing the same.
2. Description of the Related Art
With the development of light weight, thin profile, portable and high-functional electronic products, a high operation ability of HDI (High density interconnection) has become a necessary and increasingly important manufacturing process technology for the electronics industry. Among circuit boards, IC substrates and COF (Chip on Flex) have the strictest requirements for fine-patterned circuit. Traditionally, the circuit fabricating in the electronic industry mainly adopts a subtractive fabricating method which means surplus copper foil on a copper clad laminate is removed by etching process to form the required circuit patterns. In order to facilitate development of fine-patterned circuit and get rid of the adverse side-etching effect (etching factor) occurred in the wet etching process, the copper foil thickness utilized in the subtractive fabricating method has been continuously decreased for several years from 35 μm, through 18 μm, 12 μm, to current 8 μm—near the handability limit of free-standing copper foil. Therefore, not only the difficulty of fabrication increases dramatically, the development of fine-patterned circuit is also significantly limited.
Nowadays, the LCD industry adopts imported sputtering-processed FCCL products with copper thickness of 8 μm as COF raw materials. On the other hand, even having the same copper thickness of 8 μm, the FCCL products fabricated by the casting process dominant in FCCL industry, due to grain-coarsening of copper foil caused by a high-temperature casting process, are limited to applications with line width/line space (L/S)≧30/30 μm which does not meet needs of the current LCD industry. However, due to the high prices and poor performances (for example excessive pinholes, low and annealing sensitive peeling strength), the imported sputtering-processed FCCL products not only adversely affects the cost competitiveness in the short run, but also significantly affects the future development of the LCD industry in the long run for the incompleteness of the supply chain. Therefore, it needs to be exigently improved. In addition to the sputtering process, two other fine-patterned circuit fabricating methods including the so-called thick copper microetching thinning method and ultra thin copper foil (copper foil attached with carrier foil) method, are also considered but excluded by LCD industry for difficulty in control of copper foil thicknesses and a problem that the carrier foil cannot be peeled off (detach) after a high-temperature (≧300° C.) pressing operation respectively.
In conclusion, in considering the completeness of the LCD supply chain and the future development of the FCCL industry, it is necessary and exigent to enhance the existing casting process dominant in FCCL industry to meet COF application requirement.